This invention relates to an improvement of a magnetic wedge for use in an electromagnetic device, particularly a rotating electric machine, and more particularly to an improvement of a magnetic wedge with a magnetic member molded with a plastic member.
As well known, a winding of the rotating electric machine is received in a core slot, and to this end the wedge is provided at the opening of the core slot.
This wedge is generally constructed of a non-magnetic material having a small permeability, but in the rotating electric machine with a small air gap between a stator and a rotor, e.g. an induction motor, the wedge having a certain magnetic property is used in order to restrain some ripple of magnetic flux distribution in the air gap due to the presence of the core slot and core loss or increase of an excited current due to the concentration of magnetic flux to core tooth portions. Such an wedge is generally called a magnetic wedge. In order to make uniform the magnetic flux distribution in the air gap between a stator and a rotor and the core tooth portions, the magnetic resistance for the magnetic flux passing from the core tooth portion to the air gap side via the wedge should be as small as possible, and on the other hand, the magnetic resistance for the "leak magnetic flux" passing from one tooth portion to the other tooth portion via the wedge due to the difference in the magnetic potentials at the core tooth portions at both ends of the core slot should be as high as possible. In other words, the magnetic wedge only having a strong magnetic property (i.e. large permeability) is insufficient and it is desired to have magnetic anisotropy passing the magnetic flux only in a specific direction.
Known examples of the construction of such a magnetic wedge having magnetic anisotropy are as follows.
In one example, magnetic members are arranged only in the neighborhood of the tooth portions of both sides of a core slot in its width direction, and these magnetic members are unified by connection means of non-magnetic material or plastic member such as resin. The magnetic wedge having such a construction is dislosed in, for example, Japanese Utility Model Publication No. 5659/1939 and Japanese Patent Publication No. 1332/1935 (Japanese Patent No. 111,452).
In another example, flat magnetic particles, with the direction of their flat plane aligned with that of the thickness of the wedge, are molded by resin, or the like. This construction is disclosed in, for example, JP-A-52-6906 (1977).
Although the magnetic wedge used in an electric rotating machine is desired to have a magnetic anisotropy as mentioned above, from the viewpoint of the magnetic property, when also considering the actual use, it must have mechanical strength enough to be able to serve as a winding support, which is in intrinsic function of the wedge, and be easy to fabricate.
The above mentioned prior art wedges, however, have inadequate mechanical strength and are difficult to fabricate. And since the electromagnetic force has been increased with the development of a larger capacity electric rotating machine in recent years, increased mechanical strength is necessary.
More specifically, in the prior art example in which magnetic members are arranged only in the neighborhood of the core tooth portions at both sides of the wedge in its width direction and these magnetic members are unified by connecting them using non-magnetic materials or molding them of a plastics material, it is difficult to assure the mechanical strength at the connection portion between the magnetic members and non-magnetic materials and the resultant structure is likely to be complicated.
In the prior art example wherein the longitudinal direction of the flat surfaces of flat magnetic particles or the magnetic lines is aligned with that of the thickness of the wedge, it is difficult to uniformly align the magnetic particles or magnetic strips in the length direction of the wedge and also difficult to assure a mechanical strength that is sufficient to support the winding since the strength for the shearing force, which is important to fix the winding more stably in the slot is necessarily adapted to depend on the strength of the plastics member made of a suitable synthetic resin.